Art of producing continuous film from plastic material



June 23, 193e. H, A EVEY 2,045,328

ART OF PRODUCING CONTINUOUS FILM FROM PLASTIC MATERIAL File'd 001'..l25, 1951 4 Sheets-Sheet l June 23, 1936. H.' A. LEvEY 2,045,328

' ART .OF PRODUCING CONTINUOUS FILM FROM PLASTIC MATERIAL Filed oct. 2s,1951 v 4 sheets-sheet lJul'm: 23, 1936.' H, A. LEVEY 2,045,328

ART OF PRODUGING CONTINUOUS FILM FROM PLASTIC MATERIAL muy 7 Minn" O QJune 23, w36.,- H A, VEY 2,045,328

ART OF PRODUCING CONTINUOUS FILM FROM PLASTIC'MATERIAL vFiled 0G11. 25,1931 4 SheetS-Sheet 4 Patented June 23, 1936 v UNITED. STATES ART A OFPRODUCING CONTINUOUS FILM FROM PLASTIC MATERIAL Harold A. Levey, NewOrleans, La. Application October 23, 1931, Serial No. 570,127

12.Claims. This invention relates to the production ofy sheets or filmsfrom various plastic materials and refers more particularly to a, methodand apparatus for the continuous conversion into film, of viscoussolutions of plastic material and a more or less volatile solvent,forexamplef solutions of cellulose and cellulose derivatives, such ascellulose acetate, cellulose esters or ethers. The invention is alsoapplicableto starch and starch derivatives, gelatin and gelatinsolutions, resinous plastic solutions and the like.

'I 'he invention is particularly adapted for the continuous productionof relatively thin films which are of substantially uniform of uniformthickness, density, etc.

The invention will be fully understood from the following detaileddescription in conjunction with the accompanying drawings.' in which:

Fig. 1 is a somewhat diagrammatic elevational view, partly incross-section, of an apparatus for producing illm in accordance with thepresent invention. l-

Fig. 2 is amedial longitudinal sectional view of the apparatus vshown inFig. 1. y.

Fig. 3is an end elevational view of a spreading or extruding nozzle forforming the plastic solution', in the form of a film, upon the surfaceon y which it is hardened to produce the nished nlm.

l suitable means for driving the `film carrying belts.

Fig. 4 is a fragmentary front elevational view of one end of the nozzle'shown in Fig. 3, taken onlinelofFlgS.' "E

Fig. 5 is a transverse sectionalview of the nozzle shown in Fig. 3.

Fig. 6 is an enlarged fragmentary vertical longitudinal sectional viewtaken on line 5 of Fig. 3.

` Fig. 7 is a transverse sectional view of a modifled form of nozzle. y

Figs. 8 and 9 are fragmentary sectional views showing diierent ways ofanecting a close and leak-proof fitbetween the outer surface and thesurface upon which the film is formed, andthe end walls of the nozzle.

Fig.` lOlis a fragmentary cross-sectionalyiew of one form ofilm'spreading blade, or bar. Fig. 1l is aside elevational view of meansfor supporting the end wall of the nozzle upon the surface upon whichthe film of viscous material L 30 are closed bymeans o f strips whichdepend is cast.` l

Fig. 12 is a somewhat vdiagrammatic cross- 'sectional view of a modifiedform of apparatus Fig. 13l is an isometric view showing in detailReferring more in 'detaillto the rdrawings, and

more particularly to Figa 1 and.2, the numeral, f

quality, i. e.

Y form an elongated coilith'roughoutthe length I5 designates an enlargedcylindrical drum having a substantially true and unvarymg cylindricalconformation. The drum I5 is horizontally disposed and is supported upona shaftfIS by means of a plurality of spokes I'I adjacent each end 5thereof. The spokes I1 are preferably integrally secured to the innerwall of the drum vand are keyed, or otherwise tightly secured, at theirhubs I8 to the shaft I8. The shaft I6 is journalled in suitablebearingsI9 mounted upon frame meml0 bers 20 which are preferably disposed beyondthe ends of the drum. I'he drum I5 may be rotated by the followingmeans: An enlarged-wormfgear 2ljis secured adjacent to one end ofthe-shaft I6 and 'engages a worm 22 secured to a. shaft 23 l5 journaledin .supports 24. The shaft 23' is rotated lby. suitable means, such asan electric motor'25 connectedthereto by suitable gearing 26.

An annular chamber or space y2l is provided .adjacent the, inner wall ofthedrim I5 by means 20 fof a sheet metal cylinder 28 having a somewhatsmaller exterior diameter than the interior diameter ofthe drum I5. Thecylinder'`^`28 is preferably coextensive 4with: the drum 15" andisclosely fitted or sealed to the spokes I'Ifftofi'enect asub-4 25stantially gas tight fit.

The entire drum I5 is enclosed withinfa' cylindrical housing 29y havinga somewhat greater interior diameter than the exterior diameter of thedrum I5, the cylinder 29 being .at all `points 30 spaced from the drumI5 to form an' annular space or chamber 3l! therebetween.. The ends ofthe drum I 5 and the annular spaces 2l and 30 arel closed by means of apair ofA circulary disks orl plates 3i. The plates 3l are preferablytightly 35 secured toI the ends of the cylindrical housing 29 'andclosely abut the ends of the drum I5 and the Y interior cylinder 28.Thus, the drum I5 and the from the edges of the Wall of the cylinder 29to apoint just short of the 'surface of the ydrum 50 l I5. The space 3 0contains suitable heating means, for example, a large number of seriallyconnected lengths 'of pipe 34 may be mounted `therein to of the chamber30. 55

A hot fluid may be fed to the inlet end of the coil by means of a line35, the spent heating fluid being discharged from the other end of thecoil at 3 A suitable preheated gas, such as air, is supplied to theannular space 39 at a point substantially removed from the upper endsthereof by means of aline 31, (Fig. 2), which passes through one of theend plates 3|. The stream of gases so introduced through line 31 flowsto the outlet line 38 connected to one end of the space 30. Preheatedgas, such as air, may be supplied to the space 21, formed between theinner wall of the drum I5 and the cylinder 26. This air may beintroduced through a line 49 which passes through one of the end plates3I. The spent gas may be removed from the space 21 through a line 4Ileading through the other end plate 3|. The gases so introduced may bepreheated by any suitable heating means and forced through lines 31 and49 by means of suitable blowers. -It isv preferred to connect the line36 to the suction side of suitable blower means (not shown) whereby apressure slightly below atmospheric may be maintained in the space 3|).v

A suitable film forming or extruding nozzle-N is disposed in the slot oropening 32 provided in the upper portion of the cylindrical housing 29.In the embodiment shown in Figs. l and 2, the nozzle N is of a typeadapted to extrude in film form upon the outer surface of the drum I5, aheavy viscous solution containing a relatively high percentageof solidmatter. 'I'he nozzle N may be supported in any suitable manner, forexample it may be carried by a frame (not shown) in such a manner as topermit it to be closely adjusted relative to the surface of the drum`I5. The viscous filmvforming solution is supplied to nozzle N from oneor more tanks 42 through a manifold-line 43, aline 44, and into amanifold 45 leading to each end ofthe nozzle N. y The line 44 isprovided with a valve 46 and a filter 41.

VEach of the tanks 42 is provided with a. line 49 leading from a sourceof compressed gas, such as air, which `serves to force the viscoussolution from the tanks 42 to the nozzle N.

Referring more in detail to Figs. 3, 4, 5 and 6, the nozzle N comprisesan elongated rectangular chamber 50 open at its lower side which ispreferablyformed by a right angled plate 5| and a plate 52 abutting theupper side of the 'angled plate 5I. A conduit '53 ismounted between theplates 5I and 52 and isfirmly clamped between them by means of aplurality vof bolts 54 dis tributed along the length of the nozzle. Theconduit 53 extends longitudinally of. the nozzle and is provided with aslot 55 along the lower side thereof. The forward wall 56 of the conduit53 extends substantially perpendicular to the tangent of the face ofthedrum I5, while the lower side wall 51 thereof'preferably extendssubstantially parallel to the tangent of the face of the A drum, theslot 55 being defined by the inner side of the wall 56 and the edge or'terminus of the wall 51. The lower edge of the plate 5I terminates asubstantial distance short of the face o f the drum I5, while the loweredge of the plate 53 almost contacts the face of the drum I5. The loweredge of the wall 56 of conduit 53 is preferably spaced a predeterminedslight-distance (for example .01 of an inch) from the face of the drumI5 while the lower side of wall 51v almost contacts the face of thedrum-I5. It will be apparent that the bolts 54, when loosened, permitthe walls 56 and 51 to be accurately adjusted so as to produce thedesired thickness of film. The entire nozzle assembly may be carried ina suitable frame (not shown) which may be vertically adjustable relativeto the drum I5 by a suitable thread shaft, gearing, etc. The conduit 53is 5 connected at each of its ends with the manifold 45 by means of apair of conduits, one of which is shown at 56 (Fig. 5).

' An elongated plate '59 is pivotally secured, to the upper end of theangle-plate 5I by means of one or more hinges 66. The'plate 59 extendssubstantially the entire length of the -nozzle N and is angularlydisposed relative to a tangent of the drum I5. The plate 59 is of such awidth that its lower edge is capable of touching the surface of thedrumI5 a substantial'distance away from the wall 56 of thel conduit 53 (noteFig. 5). One or more compression springs 6I engage suitable lugs on theouter face vof the plate ,59 and thus tend to force the plate 59 againstthe surface 20 of the drum I5. These springs 6I may be interposedbetween the plate 59 and -suitable brackets 62 (Fig. l) secured to theplates 33 on the housing 59. It will thus be seen that the nozzle Ncontains two elongated spaces or chambers 59 and 66, 'the former beingdefined by the plates 5I and 52, and the surface Vof the drum I5, andthe latter being 35 defined by the plates 59 and 5I, and the surface ofthe drum I5. The ends ofthe nozzle N (and the spaces 50 and 66) may beclosed by means of suitable removable plates 66. A It is preferred togroove the inner sides of plates 59, the upper leg of plate 5I, andplate 52, along their edges, to form grooves 61 into which may be ttedthe plates 66, The plates 68 may be secured in any suitable manner,however it is preferred to provide a plurality of compression springs 69which exert a substantial force against thev outer side thereof 'atvarious points, (note Figs. 3 and 4). The plate 66 is thus forced intotight fitting relation with the shoulders formed by the grooves 61 onplates 59, 5I and 52. The lower` edge of the plate 66 'is preferablyconcavely curved on a radius corresponding to the radius of the drum I5,whereby its loweredge at all points closely fits against the surface ofthe drum I5. It is preferred to form the plate 66 of brous material.While any suitable means may be employed for the purpose of maintainingthe lower edge 63o! plate 59 in thedesired spaced relation relative tothe surface of the drum, -it is preferred to employ the plate 66 as ameans for so spacing 00 the lower edge of plate 59. To this end thelower forward end'of plate 66 may be provided with a protruding taperedfoot 10 which extends through a notch 1I (Fig. 4) provided in the loweredge 63 adjacent the end plate 59, the lower edge of 65 the footID-resting upon the surface of the drum I5. It will thus be seen that byextending or l 4'retracting the foot 16, the' clearance of the edge 469is provided with a threaded bore which receives a bolt 12 which extendsthrough a vertical slot in plate 52. The inner side of plate 52 isprovided with a counter-slot -13 which receives a. 75

nut 14, the slot 13 being only wide .enoughto permit the nut 14 to bemoved vertically therein while preventing it from rotating. The bolt 12-engag'es thenut 14, and is provided with a nut 15 on the portion thereofwhich protrudes through the plate 52. By means of this-particularstructure plate 68 may be moved toward or away from the plate 52, thusextending or retracting the tapered'foot 10 relative to the lower edgeoi plate 59 to accurately vary the spacing of the lower edge of thelplate 52 relative to the surface of the drumA I5. l

In the operation of the device, a suitable solution of viscous materialwhich upon evaporation of the liquid solvent admixed therewith assumes ahard plastic state, is supplied to the tanks 42.

Such a'solution may suitably comprise celluloseV through lines 43, 44.and 45, the filter 41 andl the conduit '53 in the nozzle N. It ispreferred the desiredsadjustmentsfhave been made, thej to use the tanks42 alternately, thusl fresh material may be supplied to one of the tanks42, while the nozzleN is supplied with material from the other tank. Inthis way air, or other gas, which may be admixed with the viscousmaterial, may be permitted to escape therefrom before the material isfed to the nozzle N.'l The ow of the material to the nozzle N may beclosely controlled bythe valve 46.

` Prior to beginning the feed ofthe viscous material to the nozzle N,the drum I5 is warmed or heated to a suitable operating/temperature. To'this end, a suitable heated iluid, such as water, is circulated throughthe coil in the space 30, and 4a heated gas, such as air, is introducedto the lchambers or spaces 30 and 21by means of the lines 40 and 31. Thespent gases are withdrawn from the chambers or spaces 30 and 21 throughthe lines 38v and, 4|. The clearance of the lower edges of the wall 5 6and the blade 59 is carefully adjusted. 'Ihe lower edge of the wallv 56-is al- -ways spaced a substantially greater distance from the surface ofthe drum I5 than is the lower edge 63 of the spreading'or forming plate59. After rotation of the drum is begun. The drum as tionof pressure,rises to the surface of the layer viewed in Figs. '1,3, 5 and 7 isrotated in a counterclockwise direction;

When the drum has reached the desired temperature, the valve 46 in line44 is opened and the viscous material ows to the nozzle. 'I'he pressuremaintainedwithin the tanks 42 is suillcient to cause a comparativelyeven flow of the material to the nozzle-N. The viscous material flowsthrough the slot 55 and coats the surface of the drum I5, movingth'erepast. The lower edge of the vwall 56 of the conduit functions tovgauge the thickness of the layer of material applied to the drum. Asthe layer 23* of migerial leaves theconduit 53 any entrained air orpockets o f solvent vapor tend to rise to the surface thereoi in thelform of small bubbles. Also any solvent `which becomes vaporized,because oi the reducof viscous material. By the time Jthe layer of.material reaches the edge 53 of the blade 59 substantially all vapors.and gases have either escaped therefrom, or have accumulated in theform of bubbles adjacent the upper surface thereof. As the viscous layer13Il passes under the edge of blade 59 the upper portion thereofcontaining air or gas bubbles is prevented from pass- 5 ingv therebeyondand the layer of material is reduced to the desired uniform thickness,the upper portion containing the bubbles accumulating along the innerside of the plate 59, as shown at 14.

It will be noted that the blade 59 is disposed at an acute anglerelative to the layer of material advancing toward it from the conduit53. This angular disposition o f the blade I have found is extremelyeffective and forms a layer of material of 4substantially maximumdensity which is substantially free from variations in thickness andlongitudinal lines or undulations even with the use of plasticlsolutions of high viscosity. While the angle of the blade 59 may varydepending upon various conditions of operation,the type of materialtreated, etc., I have found that the -best re'sults are secured when theangle of the narily, an angle of 30 will "be found to give.

optimum results. -Also, I have found that the outer or retiring edge 64of the blade 59 should be substantially perpendicular .to a tangentprofjected on the suface of the drum I5 at a point 30* directlytherebelow. However, comparatively satisfactory results may be obtainedwith a. 5-l0 variance to either side of the perpendicular.

The substantially even layer of material enters j the space 3|! whereinit is subjected to the body or 35 'atmosphere of warm `gas therein whichbecomes heated by the coils 34. The layer of material is also warmed bythe heat derived from the drum I5, the entire wall ofthe drum beingwarmed by Vthe warm 4gas circulated along its inner side 40 through thechamber 21. Under the influence of the heat and the warm gases,thesolvent evaporates from the layer of viscous material, and by the timeit approaches the other end of the -space 30 -it is substantiallycompletely hardened into-a 45 dry film. It will be seenl that the illmof viscousmaterial is first passed through a substantially quiescentbody or atmosphere of vwarm gas, there being substantially nocirculation of gas between the inlet '40 and the end of the space SI1-atwhich 50 the freshly cast illm enters. As the film becomes somewhatdried, and consequently more firm, it reaches the zone of circulatinggases, i. e., the portion of the space between theinlet 31 and theoutlet line .38. This constant stream of fresh 55 gases passing overthe'partially dried illml rapidly absorbs'the solvent vapors and thusmaterially speeds the drying operation.. 'I'he dry film is re;r4moved-from the drum I5 after it passes t e "endA of the heated chamber39. In practice tpefllm 60 is threaded under a suitable -roner 15 ard iswound upon a suitable roll 13, as fast as it is formed.

The heat supplied to the rim of the drum by means of the warm'gasespassed along its inner 65. surface, through the chamber 21. is at leastsufficient to offset the coolingeifect on the drum I5 plasticize'rs,resins,

-.Ihus loss of the solvent is avoided, and the evaporated solvent mayall be passed to a suitable recovery Operation.

'I'he hot heating fluid ows through the coil 34 in a direction oppositeto the direction of rotation of the drum I5. By means of the hot fluidflowing through the coil 34, the atmosphere of gas surrounding the drummay be maintained at substantially the optimum temperature, the coolingeifect on the warm gases by the evaporating solvent being substantiallyentirely counteraoted by the heat supplied to such gases by thecountercurrently fiowing'heating fluid in the coil 3l. By owing the hotfluid through coil 84 in a direction counter to the direction ofmovement of the film through the space 38, the temperature of the warmatmosphere of gases to which the drying film is exposed, during itsmovement through the space 80, may be progressively higher in thedirection of movement of the/film. The hot fluid in coil 34 alsofunctions to warm any cool airy which leaks into the chamber 30 -becauseof the reduced pressure therein. It will be seen that the coil 84supplies suillcient heat to maintain the gases at the most effectiveoptimum temperature throughout the chamber or space 30.

Thus, the gases introduced atA 31 are at the optimum temperaturerelative to the state of the film at this point, and may be heated, ifnecessary, to a higher temperature as they progress toward the outlet 88and the point of removal of the finished fllm. The air leaking between'the plate 33 and the freshly deposited layer of plastic material, may beheated to the optimum temperature by the fluid in coil 3l. It will beseen that by means of the coil 34 various temperature conditions mayreadily bev maintained in the chamber 80. Thus the freshly applied layerof material may be subjected to a temperature sufficient to effect theImost rapid evaporation of the solvent without deformation of the layerof material, and as' the film progresses toward the point of removalfrom the drum Il, it may be subjected to increasingly highertemperatures.

While the nozzle N heretofore described may be employed for theextrusion of various types of plastic of a film, it is especiallyadapted for use in connection with extremely heavy or viscous uids, forexample, 500 second cellulose nitrate, or an equivalent solution ofcellulose acetate consisting of as high as 30% solid matter, includingthe acetate, stabilizers, etc. By meansof this type of nozzle, films ofa thickness of l mil. and upwards may be effectively produced from suchviscous materials upon the drum I5.

In Fig. 'l I have illustrated a modified form of nozzle M wihch isadapted'ifor use in connection withthe formation of relatively thinfilms having a thickness of lessthan 1 mil. for

' example 1/2 mil., or 0.0005 inch.

For effecting the production of such relatively thin films I have foundit desirable to employ less viscous solutions than those heretoforereferred to in connection with the use of fluid upon a surface for theformation nozzle N. For example, in the production of. lm of 1/2 to 1mil. in thickness from a solution of cellulose acetate andy acetone,best results are secured when not more than 20% solid material isemployed in the mixture, and preferably when not more than about 16% ofsolid material is employed in the mixture to be used.

The nozzle M shown in Fig. '7, like the nozzle N, is mounted over the'top side of the drum I5, being carried in af suitable supporting frame(not shown) and mounted therein for close vertical adjustment relativeto the surface of the drum. This nozzle comprises a right angled plateWithin which is carried a conduit 8|. The latter is preferably securedby means of a plurality of cap-screws 82, which pass through the sidesof the angular-plate 80 and engage threaded apertures formed in theconduit 8|. The upper portion of the front wall of the conduit 8| isprovided with an elongated slot 83. The conduit 8| is connected to themanifold 45 in a manner similar to the conduit -53 in nozzle N. The freeend of the top leg ofthe plate 80 is'connected by means of, one or morehinges 84 with a forming plate 85. This plate may be of the same generalstructure as the plate 59 in nozzle N, and` may be forced toward thedrum |5 by one or more springs Gla. The rear Wall of the nozzle M may besealed relative to the surface of the drum |5 by means of a soft fibreplate 86, which extends therebelow. The ends of the nozzle M may beclosed by means of Walls similar to the walls 68 of nozzle N, andsimilar means may be employed for spacing the lower edge of the bladefrom the drum l5.

It will be noted that in the nozzle M the material is not applied to thedrum I 5 in a'relatively thin layer which layer is reduced by the blade(as in nozzle N). is maintained in a substantial body within-the porizedsolvent bubbles.

In Figs. 8 and9 I have shown slightly modifled outer surfaces for thedrum l5. In Fig. 8 the outer portion of the drum is of reduced diameterto `form a square shoulder or onset against which the end wall 68 of thenozzle may.

t. -In the embodiment shown the end wall plate 68 is lined with a thinlayer 9| of relatively soft fibrous material. In Fig. 9 the marginalportion of the drum |5 is raised as shown at. 82. The Alower edge of theend wall plate bears uponv this portion .92. The inner side of the plate68 carries a soft fibre plate 93 which extends therebelow and againstthe surface of tlzie drum i5 within the raised marginal portion 9 InFig. 10 is shown a blade for distributing or forming the layer of fluidmaterial to be formed into film. This plate is in general similar tofthe plates 59 and 85, but has an acute lower edge instead of aflattened one. This Instead, the viscous materiali-" "254e "'f nozzle Mand almostcompletely fills the interior blade, like blades 59 and 85, isset at an angle the end walls 50 of the nozzle upon the surface of thedrum I5. The lower edge of the endwall plate 68 rests upon the top sideof a frame mem ber |00. The lower side of the frame is arc- -i uate,having a radius of curvature the same as that of the drum I5. 'Ihislower edge of frame A |00 almostcontacts the surfacel of the drum I5.vThe 'frame |00 is maintained in such relation to the drum I5 by meansof a pair of hardsteel l l0 wheels I0| secured to either end of theframe |00. 'I'hese wheels support the entire weight of each end of thenozzle and because of their rolling action avoid substantial wear of thedrum -I 5. It will be .understood that the outer surface of the drum I 5should be extremely. smooth and of a true cylindrical conformation.Also, the

' outer surface of the drum as weil as the parts of the nozzle, thetanks 92 and the various pipe N lines, valves, filters, etc. which comeintocontact with the viscous material, to be formed into nlm, may beconstructed of, or at least coated,

l with substances which are resistant to corrosion by such material. Forexample, nickel. Monel 85 metal, silver and nickel-chrome iron alloyshave been found to be resistant to cellulosev acetate mixtures. It ispreferable to maintain the mix-4 ture of material within close vrangesof tempera.-A

ture during its passage. to and through the nlm forming nozzle. Suchtemperatures may vary to a certain extent, depending, of course, luponthe particular mixture of substances employed. For

example, the afore-described cellulose acetateacetone solution,containing 30% solid matter,

should be maintained at about 10o to 120,

during its flow to the nozzle.

Figs. 12 and 13 show an apparatus generally similar to that shown inFigs. 1-11 inclusive, which is provided with. a secondary drying sys-4,0' tem for the nlm. In this embodiment, the nlm is removedfrom the`rotary drum before-it has entirely dried and'ls lsomewhat plasticandlwhile in such condition it is. suitably longitudinally drawn orstretched and thereafter completelydried in a warm atmosphere of gases.In order to simplify the description, the various parts of drum I5.The-housing |05 is provided. with suitable side walls (not shown)" whichare fitted betweenthe exterior of housing 29'l andv the.A

housing |05 in a substantially leak-proof manner. 'Ihe upper side ofthe'housing |05 is cut away to forman elongated transverse slot oropening corresponding to the opening 32,* vin the i5 housing -29 inwhich is located the' feed nozzle'4 Nl. The resulting open ends formedby this cut- .away portion are closed by pairs of elongated strips orplates |05 and |01, each strip I00vde- Apending from the housing |05 and.each strip', |01

0 extending upwardly from the exterior of the housing 29", the freeedges of each pair of strips |00 and I 01 being spaced apart to vforma'slot `V `...|00 through which a strip of iilmmay be passed. One end ofthe housing |05 is connected to a I., conduit |00 leading from asuitable source ofg betweenthe two setsof belts or cords IIS.

warml gases and the other end of the housing |05 is connected to anoutlet conduit ||0, wherebywarm gases may be circulated through thehousing |05 in a direction of now corresponding tothe .direction ofrotation of' the drum |55.. 5 The conduit |`|0 may lead directly to theconduit I0* whereby the warm gases .from housing |05 kmay be passed to|thespace -30s between' housing 29* and the drum I5, or the line |I0ymay lead .directly to a suitable operation for recovering 10 solventvapors from the warm gases.

A pairofelongated rolls III. and ||2 are provided adjacent the point ofremoval of ilm from the drum I5, the rolls being adapted to engage.between them the sheet or' strip of illm'formed 16 upon the drum I5".Either, or preferably both. of the rolls III and ||2 .are positivelyrotated by suitable mechanism (not shown) at such a speed that thevelocity 4of their faces is substantiauygreater than the velocity of theface of the 2,0

drum I 5*, for example, the surface velocity of the rolls III and |I2may be from tato' 2% greater than that ofthe drum I5". The interior ofthe housing |05 is provided with suitable film conveying means, forexample, a plurality of 25- opposed endless cords or'belts ||3 may beprovided therein. These' belts or cords may suit# ably comprise twoadjacent sets, one side of each loop of belting in one set of beltscontacting one -v side of each belt loop of the other setri The belts 80I'I3 are looped over suitable rollers provided in the ends of thehousing' |05, rollers II4 and ||5 engaging one set of belts I|3and-,rollers III and ||1 engaging the` other set of belts I I3.y Thebelts ||3`are supported and guided Iintermediate'the 86 rollers II4,II5, II6 and III by a plurality of spaced idling rollers I|8. The beltsare preferably driven by suitable vmeans (not shown) at `a l speedsubstantially equal to lthe surface speed or velocity of the tensioningon stretching rolls. III o and H2; The operation of the deviceillustrated in Figs. 12 and 13 is substantially similar to that of theAapparatus shown in Figs. 1-11. Thus, a layer or film of a'viscous solution of cellulose acetate, or 45 like material, iis deposited-uponthe surface of the rotating drum -I 5 by the nozzle N, the fresh nlmbeing carried first through therelatively quiescent zone of warm gasesmaintained in the space 30 formedby the'housing 29'*4 and then throughthe 50 zone of circulating or flowing warm gases in the remainingportion of the space 30. The operation is 'so controlled that bythe timethe material reaches the end oi the space 30* it is partiallydryfhowever it is desirable thattheJ 65.

nlm besuiiicient'lydried that it possesses considerable strength vand isnot sticky or "tacky". The lm isv drawn as a continuous strip aroundIthe idling' guide-roller 15 by the tensioning or stretching rollersA||| and .|I2 between which 00 it is fedg.. The film is elongatedorstretchedffbef causel of the differential of surfacevelocities '.betweenthe'rollers III and ||2 and the drum I 5". The stretched ilm passes frombetween the rollers III and U2 throughv the slot I00in1the 65 end of thehousing |05 adjacent the rollers '|I |1- and' I2 and is carried-throughthe housing |05 The nlm is passed from the other end of'housing |05through the slot |00 in the end wall overl an 70 idlingguide roller II9and thence to a suitable reel orspool |20 upon which it is wound. .Thehot gases flowing through housing I 05 preferably f iiow in a directioncounter-to the direction of s movement of the film therethrough andcontact the film on both sides thereof to completely dry it.' Thestretching or elongating of the film before it has completely dried notonly removes wrinkles and other similar irregularities in the but alsoimproves the tensile strength of.

the film. i

` I claim: 1. In a device of the class described, a movable continuoussmooth surface adapted to receive ay coating of viscous film-formingmaterial, means forv moving said surface in a predetermined pathof'movement, a film 'forming blade associated withA the said surface,said blade being inclined at an angle of from 25 to 30 relative to thesaid forming surface in a direction opposite .the direction of movementof said forming surface, and

- means for applying viscous .material to the surface of heated inertgas, said last mentioned gas being f of said forming surface, closely inadvance of said film`forming blade.

2. In a device of the class described, a smooth surfaced forming memberadapted to receive a coating of viscous material, a lm forming bladeclosely beyond said forming member, means for movingsaid forming memberpast said blade, and means for applying viscous .of said blade, the sideof said blade from which said forming member retires being within of theperpendicular relative to the forming surface.4

3. In a device surfaced forming member adapted fto'receive a coating ofviscous material, a nlm forming blade closely beyond said forming membermeans for moving said forming member past said blade, and

means for applying viscous material to the said surface of said formingmember at a point ahead `of said blade, the' side of said blade towardwhich said forming member approaches being inclined atranangle of 25 to'35 relativeito said forming surface in a direction opposite to thedirection of movement of saidforming member and the side of said bladefrom which said forming member retires being within 5 of theperpendicular relative to the forming surface.

4; The method of producing continuous film from viscous material whichcomprises applying a layer of viscous material to the surface of oneside of a forming member, passingfsaid layer through abone of heatedinert -cmiescent gas, and then passing said layer through a second zonemovedin the direction of movement of said film, and being progressivelyheated to a higher,` temperature during itsmovement through said sec-lond zone.

5. The method of producing continuous nlm -from viscous material whichcomprises applying a layer of viscous material to the surface of oneside of a forming member, maintaining a heated zone along the oppositeside of said forming member, and passing said layer through anindependent zone of heated inert gas, said gas being moved 1n thedlreeunpr movement of said ma; and being progressively heated to ahigher' temperature during its movement through said zone.-

6. Apparatus for producing continuous film from viscous material whichcomprises a movable continuous forming surface, means for applying amaterial to the said surface of said forming member at a point ahead ofthe class described, a smooth layer of viscous material thereto, acompartment adapted gas, means for moving said surface therethrough, asecond compartment adapted to maintain a zone of moving gas, means formoving said surface therethrough, means for moving gas therethrough in adirection of movement of said forming surface, means for progressivelyheating said gas to a higher temperature during its progress throughsaid compartment, and means Yfor removing said layer from said' formingsurface.

'1. Apparatus as set forth in claim 6 in which said forming surface isindependently heated on the side opposite that carrying the layer ofviscous material.

to maintain a zone of heated quiescent 8. Apparatus as set forth in.claim 3., in which said film-forming blade has a flattened lower edge ofsubstantial width and lying substantially in the plane of the surface ofthe drum. i

9. The methodr of producing a very thin film from viscous material ofthe cellulose ester type which comprises applying a coating of such maofmaterial to undergo drying upon said surface sufficient to free it fromthe surface, removing the resulting film from said forming surfacebefore it has completely dried, and passing it through a zone of gasessubstantially warmer than the nlm in such manner that the gases contactboth sides of the nim, and wherein the film is uniformly dried upon bothsurfaces thereof, to produce a substantially completely driednon-curling film.

10. The method as set forth in4 claim 9 in which the partially dried nlmis longitudinally stretched.

terial to a forming surface, causing the coating 11. An apparatus forforming a film from vis`- cous material comprising a heated movablecontinuous film-forming surface, means for maintaining a liquid body ofsubstantial thickness and width upon and in contact with the nlm-formingsurface, and a film-forming blade in spaced relation to said formingsurface" and closely adjacent to said liquid body, the side of saidforming member being inclined at an angle of 25 to degrees from' saidnlm-forming surface and in a direction opposite to the direction ofmovement l`thereof,y and the 'side of said blade from which said formingsurface retires being within -nye degrees of perpendicular relative tosaid surface.

v angle of 25 to 35 degrees from said nlm-forming surface and in adirection opposite to the direction of movement thereof, and the' sideof saidl blade from which said forming surface retires being within fivedegrees of perpendicular relative to said surface.

naraom A.

